Quests: main quest items no longer refused, restart resets bit-field variables

AddMainQuestItem refused every new main quest item once the list held an
entry with script id 0 (scripts give such items); the Goldbeeren of quest
402 were picked up and lost. The script id test is patched out.

Quest variables are bit fields (op 0x44 sets a bit): the quest giver
restart now writes the values directly, 0 and 1 (available) for the
variable named after the quest.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/quests.md

@@ -196,7 +196,8 @@ Dialogs without a quest (healers, closed shops: `geschlossen101`,
   4 trigger area, 0x0f end quest, 0x14 start quest (#id), 0x17 named
   position, 0x1a dialog text, 0x35 book text, 0x3a / 0x42 if / else if
   (0x49 var == n, 0x40 "@npc"), 0x3c dialog answer (text, label), 0x3f
-  compass, 0x44 set variable, 0x48 move NPC, 0x56 dialog state.
+  compass, 0x43 / 0x44 / 0x45 / 0x4b variables (see below), 0x48 move NPC,
+  0x56 dialog state.
 - Script NPC names: "Res:<n>" is a script id (object +0x3c, `0x44a390`); the
   quest manager maps it to the object (`0x464ec0`, map +0x7668); a spawn sets
   the entry.
@@ -227,8 +228,8 @@ load we need a repair ... if not completed or correctly running".
 `mods/questgiver.cpp`: a quest's giver is the NPC whose spawn instruction
 carries a dialog with an answer that accepts the quest (85 givers). When a
 label of a running quest runs for its dead giver, it is skipped, the quest
-restarts (failed entry at the giver, the variables only its labels set back to
-0), and once the body is gone the spawn instruction runs again. After a load,
+restarts (failed entry at the giver, the variables only its labels set back:
+0, the one named after the quest 1), and once the body is gone the spawn instruction runs again. After a load,
 an accepted quest (flag 4) without its giver gets the same. Not yet seen in
 the game (the escort of "Hetzjagd" arrived alive); see `docs/todo.md` for the
 audit of how quests can fail.
@@ -237,6 +238,40 @@ Lesson (2026-10-26): flag 1 means available, not running; a first version
 took it for running and reset 16 available quests and spawned their NPCs on
 Borf (repaired once, then saved).
 
+## Quest variables are bit fields (measured 2026-10-28)
+
+Found while repairing "Kräuter für Kräuterhexe" (402; the user knows it as
+Windgeflüster). Variables live in the quest manager's vector +0x7550 /
++0x7554 (0x24-byte entries: name[0x20], value +0x20; `game::ScriptVariable`).
+Script writes: 0x43 sets the value, 0x44 sets bit n (0x49bb30: value |= 1 <<
+n), 0x45 clears bit n (0x49c450), 0x4b adds n (0x49cc20). Conditions
+(`Script_Condition` 0x498aa0): 0x49 bit n set, 0x4a bit n clear (logged "if
+IsNotVarBit"), 0x48 value == n; a missing variable is false. The variable
+named after a quest has bit 0 while the quest is available: all 87 quests not
+yet accepted in a dwarf save had value 1, and nothing in the quest's own labels
+sets it. Quest 402: accepting sets bit 1, the berries bit 2, the reward bit 3;
+the giver's dialog offers the quest on bit 0.
+
+The quest giver restart first ran 0x44 with 0 ("variable = 0"), which set bit
+0 and cleared nothing: the giver kept saying "Zögerst du in deinen Taten?".
+A reset to 0 then matched no dialog branch at all. Now the value is written
+directly: 0, or 1 for the quest's own variable. Confirmed 2026-10-28.
+
+## Main quest items refused (request 2026-10-28)
+
+"I cannot finish the Quest Windgeflüster." The berries (type 6029) are an item
+`Region4Init` places once on the ground near the Goldbeerenbusch (op 0x5e,
+pickup label `take402`); picking it up logged "cInventoryEntry::addMainQuestItem()
+Already has mainQuestItem(6029)" and the item was gone.
+`cInventoryEntry::AddMainQuestItem` (0x5d8240, thiscall (type, script id,
+notify)) keeps {type, script id} pairs and refuses a new item when an entry
+has the same type or script id 0 (0x5d83c6); scripts that give an item
+without a "Res:" id add it with 0 (0x486bd8). The dwarf held {4609, 0}, so
+every later main quest item was refused (a bug of the original).
+`mods/questitems.cpp` removes the script id test. The save was repaired once
+by running `take402` for the hero after the load (quest accepted, bit 2
+missing); the quest then finished. Confirmed 2026-10-28.
+
 ## Escorts never left behind (2026-10-26)
 
 "I have lost a follower NPC from the quest 'Die Sklaven der Orks', it's no